Using the Internet for health purposes was associated with increased depression

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The rapid expansion of the Internet has increased the ease with which the public can obtain medical information. Most research on the utility of the Internet for health purposes has evaluated the quality of the information or examined its impact on clinical populations. Little is known about the consequences of its use by the general population.

Health-related Internet use was associated with small but reliable increases in depression (i.e., increasing use of the Internet for health purposes from 3 to 5 days per week to once a day was associated with 0.11 standard deviations more symptoms of depression, P = 0.002).

Using the Internet for health purposes was associated with increased depression. The increase may be due to increased rumination, unnecessary alarm, or over-attention to health problems.

In contrast, using the Internet to communicate with friends and family was associated with declines in depression.

References:

Image source: Wikipedia, public domain.

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Kidney Transplant Overview – Mayo Clinic Video

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Mayo Clinic emphasizes living donor kidney transplants as the best option for patients. Martin Mai, M.D., nephrologist at Mayo Clinic offers information about living donation, statistics, including the fact that living donor kidneys last longer. Half of living donor kidneys transplanted today will still be functioning 25 years from now, whereas half of cadaveric kidneys will fail in the first 10 years.

Candy and Ellen's Story.

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Sport Injuries: MRIs of hips of hockey players show abnormalities in 70% – are they clinically significant?

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A study included M.R.I.’s of the hips of 21 professional hockey players and 21 college players. They showed abnormalities in 70 percent of the athletes, even though these hockey players had no pain or only minimal discomfort that did not affect their playing. More than half had labral tears, rips in the cartilage that stabilizes the hip.

“M.R.I.’s are so sensitive,” Dr. Musahl said. “They frequently show little tears or fraying everywhere. And it is very, very common to have a small labral tear in your hip — it doesn’t mean you have to have the particular symptoms.”

References:
Personal Best - Sports Injuries - Go to a Doctor or Tough It Out? NYTimes.com.

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Blast from Europe’s medieval medical past: leeches

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From TIME:

Another blast from Europe's medieval medical past are medicinal leeches. Similar to bloodletting, leeches were utilized to draw out the "bad blood" that medieval physicians believed caused many of their patients' ailments.

In modern medicine, however, leeches are used in reconstructive surgery to provide a vacuum effect that helps stimulate blood circulation. This process is crucial to help kick start blood flow into, for example, a reattached finger.

Covered by sucking leeches! BBC video.Miichael Palin experiments with a traditional Russian health therapy in Estonian capital Tallinn by allowing a doctor to cover him in sucking leeches. Fascinating video that is definitely not for the faint hearted! Taken from BBC travel documentary, Palin's New Europe.

References:

PubMed: "Does garlic protect against vampires? An experimental study. Owing to the lack of vampires, we used leeches" http://bit.ly/IKOrY

Top 10 Bloodsuckers: Leech.AnimalPlanetTV.

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People who "drink heavily every so often" are 45% more likely to develop coronary heart disease

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Occasional heavy drinking was defined as having 5 or more standard drinks in a day at least 12 times per year. "Regular" heavy drinkers - those who averaged at least 5 drinks per day, were excluded from the analysis.

In general, moderate drinking - a drink or two per day - is considered a potentially heart-healthy habit. A number of studies have found that moderate drinkers have lower risks of heart disease than teetotalers do.

Research suggests that alcohol can increase "good" HDL cholesterol, has anti-inflammatory effects in the blood vessels and may make the blood less prone to clotting.

On the other hand, regular heavy drinking may increase blood pressure, promote blood clotting and contribute to development of arrhythmias.

References:
Occasional binges may undo alcohol's heart benefits. Reuters, 2010.

Image source: OpenClipArt.org, public domain.

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Evaluation of driving risk in dementia – practice parameter update

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For patients with dementia, the following characteristics are useful for identifying
patients at increased risk for unsafe driving:

- Clinical Dementia Rating scale (Level A)
- caregiver’s rating of a patient’s driving ability as marginal or unsafe (Level B)
- history of crashes or traffic citations (Level C)
- reduced driving mileage or self-reported situational avoidance (Level C)
- Mini-Mental State Examination scores of 24 or less (Level C)
- aggressive or impulsive personality characteristics (Level C)


Evaluation of driving risk in dementia (click to enlarge the image).

The following characteristics are not useful for identifying patients at increased risk for unsafe driving:

- patient’s self-rating of safe driving ability (Level A)
- lack of situational avoidance (Level C)

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Takotsubo cardiomyopathy (broken-heart syndrome) in differential diagnosis of chest pain

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Takotsubo cardiomyopathy (also called stress induced cardiomyopathy, apical ballooning, or broken heart syndrome) was first described in Japan 20 years ago. It is typically precipitated by acute emotional stress, hence the names “stress cardiomyopathy” or “broken-heart syndrome.”

Takotsubo cardiomyopathy is characterised by acute, reversible left ventricular dysfunction in a distribution,which does not correlate with the coronary artery blood supply. The left ventricular dysfunction occurs without obstructive coronary artery disease (CAD) and usually resolves spontaneously over a period of weeks.

The characteristic appearances on contrast angiography include:

- ballooned apical segment
- hypercontractile basal portion of the left ventricle
The appearances are reminiscent of the design of the traditional fishing pot used in Japan to trap octopus, hence the descriptive term "tako-tsubo" cardiomyopathy (octopus trap, tako tsubo). Such a trap, no more than simple ceramic jar, take advantage of the octopus’ preference for small, enclosed spaces and the security they seem to promise. They are simply left on the seabed and gathered later after octopi have had time to occupy them.

Although Takotsubo cardiomyopathy was initially considered rare, it could possibly be responsible for 1-2% of admissions for acute coronary syndrome in industrialised countries.

References:
Takotsubo cardiomyopathy. Banning et al. 340: c1272, BMJ.
Takotsubo Cardiomyopathy, or Broken-Heart Syndrome. SS Virani et al, Tex Heart Inst J. 2007; 34(1): 76–79.
Image source: Octopus trap, tako tsubo, Morikami museum.

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Super-fast automated synthesis promises to make chemistry accessible to many more – Chemistry World

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Chemists behind Lego-like automated synthesis of complex organic molecules have unveiled the next generation of this technology, cutting cycle times down by an order of magnitude from 30 hours to just three. To date, this approach has been limited because each carboncarbon bond-forming step takes about a day, wrote the team led by Martin Burke at the University of Illinois at UrbanaChampaign.

Over the last decade, Burkes group has pioneered this snap-and-go approach to synthesis, weaving together complex organic structures using SuzukiMiyaura cross-coupling reactions and N-methyliminodiacetic acid (Mida)-protected boron as the linchpin.

Burkes Mida ligand was a game-changer, stabilising boronic acids traditionally prone to decomposition due to borons Lewis acidity. By altering borons hybridisation, Mida significantly reduced unwanted reactivity, enabling sequential SuzukiMiyaura reactions for the first time under mild conditions.

The concept, says Burke, was born from a desire to level the playing field when it comes to molecular discovery. There are 8 billion imaginations in the world but, at present, those that can meaningfully participate in the search for tomorrows medicines and materials represent just a fraction of a fraction of a fraction of this greatest natural resource, he says. Automated iterative small molecule synthesis has the potential to democratise molecular innovation and thereby revolutionise the search for the undiscovered small tools that could transform our society.

While Mida was revolutionary, a key limitation of the current platform is the long cycle time of more than one day per carboncarbon bond-forming step resulting from the slow and variable kinetics of the Suzuki cross-coupling reaction. This is at least an order of magnitude slower than analogous, state-of-the-art peptide synthesisers widely used in the pharmaceutical industry.

To bring their synthesiser up to speed, they reported a major overhaul to the platform in which each step of the iterative cycle has been reimagined and re-optimised for speed, efficiency and generality.

Alongside engineering optimisations, key to the synthesisers newfound success is tetramethyl-N-methyliminodiacetic acid (Tida) boronates developed by the Burke group in 2022. Tida boronates are more than 1000 times more stable than their Mida boronate counterparts, explains Burke. This stability allows them to withstand reaction condition optimisations to the SuzukiMiyaura coupling previously reported in the literature, which speeds up the reaction but is not tolerated by Mida boronates.

This system leverages [Tidas] hyperstability, Burke adds, enabling the team to perform cross-couplings in just minutes and accelerating the rate by an order of magnitude per automated carboncarbon bond-forming step.

[This is] an impressive change in efficiency in the automated synthesis of small molecules based on iterative cross couplings, comments Varinder Aggarwal at the University of Bristol who was not involved in the study. It is currently limited to [SuzukiMiyaura] couplings but once it can do other iterative CC bond-forming reactions, it will be even more powerful.

Whether this is significant enough for widespread adoption in the pharmaceutical industry remains to be seen. I am convinced that it will be adopted over time, but there is always resistance to new technology, adds Aggarwal.

Burke also emphasises that this is not the last iteration of this technology. Peptide and oligonucleotide synthesisers revolutionised science, medicine and technology, because their continued improvement was relentlessly improved.

We are very inspired by this history and likewise plan to continue seeking relentless optimisation of this platform until the traditional synthesis bottleneck that currently limits access to small molecule innovation are shattered.

The rest is here:
Super-fast automated synthesis promises to make chemistry accessible to many more - Chemistry World

Time-resolved crystallography of boric acid binding to the active site serine of the -lactamase CTX-M-14 and … – Nature.com

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CTX-M-14 microcrystals offer perfect conditions for mix-and-diffuse experiments

The TapeDrive system26,27,37 was applied to collect serial diffraction data at the beamline P11, PETRA III/DESY, to explore the kinetics and structural intermediates of ligand binding to the -lactamase CTX-M-14. As a result, protein structures with delay times of 5010,000ms and a resolution range of 1.402.04 were obtained. For this purpose, CTX-M-14 microcrystals were mixed with boric acid to initiate the binding process, and diffraction data were collected after distinct pre-set delay times. To monitor the formation of a diester, microcrystals were pre-soaked with boric acid and subsequently mixed with glycerol and again diffraction data were collected after distinct delay times. The obtained data can reveal the time evolution of populations and, as for all mix-and-diffuse serial crystallography data collections, can represent multiple states in one structure. The delay times, the corresponding PDB entries, the obtained diffraction quality and model refinement statistics are summarized in Supplementary Tables1 and 2. In our own unpublished experiments, macro-crystals of CTX-M-14 were soaked with boric acid and diffraction data were collected by conventional rotation crystallography at cryo-conditions. Glycerol was used as a cryo-protectant, and thus the cyclic glycerol boric acid diester (GBE) in the active site described here has been observed (PDB code 8r7m). However, a time-resolved analysis of the processes seemed very intriguing due to the two sequential reactions. To observe the reactions via time-resolved crystallography applying the available TapeDrive setup of CFEL at PETRA III, DESY, the reaction rates needed to be decreased. In terms of pilot investigations, we observed that kcat is reduced approximately twofold at pH 4.5 compared to pH 7.4. Therefore, the relatively low pH 4.5 applied for the crystallization conditions supported the optimization of time-resolved diffraction data collection of CTX-M-14, although it does not correspond to the physiological pH value. The asymmetric unit of CTX-M-14 crystals contains one monomer with the active site region solvent accessible. The Matthews coefficient of the crystals is 2.153/Da, corresponding to a solvent content of 43%. The solvent channels in the crystal lattice allow rapid diffusion of low molecular weight ligands to the active site, scoring the CTX-M-14 crystals to be ideal for time-resolved serial crystallographic investigations, applying the TapeDrive mixing approach27. Furthermore, the small but excellent diffracting crystals of CTX-M-14 with dimensions of 1115m have a relatively small ligand distribution period within the crystal lattice and due to short diffusion times exhibit sharper delay time points compared to larger crystals38. As a reference, the TapeDrive was also used to collect serial data of the native CTX-M-14 crystals. The occupancies of boric acid and its glycerol diester in the active site obtained after different mixing time points were refined and compared to discuss the stepwise rearrangements in the active site in detail below. To avoid correlation of occupancies and B-factors during refinement, care was taken that between datasets of adjacent time points the individual B-factors of the respective ligands did not differ more than the Wilson B-factors and the average B-factors (Supplementary Fig.2).

CTX-M-14 has a crucial anion-binding site (Fig.1) close to the active site residues that is occupied by the carboxylate of -lactam substrates39. In the native enzyme, this site is occupied by a tetrahedral anion, such as a phosphate (PDB code 4ua640) or a sulfate (PDB code 7q0z13), as in the structures we refined (Figs.1 and 2). In a structure of CTX-M-14 in complex with ixazomib/bortezomib (PDB code 7q11/7q0y13), the inhibitor does not directly occupy the anion-binding site, but still displaces the bulky tetrahedral anion, which is replaced by a smaller chloride to balance the charge13.

a Cartoon plot of the CTX-M-14 -lactamase from Klebsiella pneumoniae and close-up views of the active site in surface representation of b the native constitution with a sulfate ion (SO4-A magenta; SO4-B yellow) in the anion-binding site, c with bound boric acid (BAB, pink) and a sulfate ion, and d with bound glycerol boric acid diester (GBE, pale green). BAB (c) and GBE (d) complex structures are shown with mixing delay times of 10s, respectively.

Stick and cartoon representation (left) as well as 2D-LigPlot+ representation (right) of the active-site amino acid residues highlighting the hydrogen bond network in the native form (a), with bound boric acid (10s, BAB) to Ser70 (b) and with the bound glycerol boric acid diester (10s, GBE) (c). Each equilibrium state is displayed individually without overlapping with the initial states. BAB and GBE oxygen atoms are labeled in red. Potential hydrogen bond distances () are indicated by dashed lines.

The rotationally disordered sulfate occupies two slightly displaced alternative positions in the native enzyme (SO4-A and SO4-B, S to S distance of 0.4, Fig.1). The alternative sulfates (A/B) are coordinated via hydrogen bonds with the side chains of Ser70 (3.1/3.4), Thr235 (3.1/3.3) and Ser237 (3.4/2.8) as well as the main chain nitrogen of Ser237 (3.1/3.2) (Fig.2a). SO4-B forms additional hydrogen bonds with side chains of Ser130 (2.9) and Lys234 (3.2) (Fig.2a). During boric acid binding, the sulfate is reoriented in such a way that it is more distant to the Ser70 side chain and coordinated by hydrogen bonds with the side chain hydroxyl groups of Ser130 (3.1), Thr235 (3.0) and Ser237 (2.9) (Figs.2b and3). In addition, the boric acid O2 (2.6) can act as a hydrogen bond donor for the sulfate. The esterification with glycerol finally displaces the sulfate ion, since the equivalent O2 of the cyclic diester cannot act as a hydrogen bond donor anymore and due to steric competition (Fig.2c). In the electron density maps substantially reduced density is observed at this site (Fig.4). After complete formation of the cyclic diester with boric acid and glycerol, a water molecule (OW357) occupies the position of the anion-binding site. Unlike the sulfate ion, the OW357 can act as a hydrogen bond donor and forms a hydrogen bond with O2 of GBE (2.7). The water molecule OW357 is further stabilized by a hydrogen bond with the hydroxyl group of Thr235 (2.8), as well as a weak hydrogen bond with the main chain carbonyl of Thr235 (3.5).

Polder electron density (contoured at 5 , green mesh) of the active site Ser70, the sulfate ions and bound boric acid are shown at different delay time points after mixing microcrystals with boric acid. The 1h soak structure was obtained with the TapeDrive after microcrystals have been soaked in boric acid for 1h and shows that almost no further increase in electron density is observed after 10s. BAB and GBE oxygen atoms are labeled in red. Potential hydrogen bond distances () are indicated by dashed lines.

Polder electron densities (contoured at 5 , green mesh) of the active site region of CTX-M-14. Microcrystals pre-soaked with boric acid and mixed with glycerol prior to serial diffraction data collection applying the TapeDrive setup at beamline P11, PETRA III/DESY, observing time-resolved the ester bond
formation between glycerol and the Ser70 borate ester. The sulfate anion present in the native conformation is displaced upon binding of GBE and finally replaced by solvent water OW357. BAB and GBE oxygen atoms are labeled in red. Potential hydrogen bond distances () are indicated by dashed lines.

A direct comparison with recently approved inhibitors such as relebactam (PDB code 6qw841) and avibactam (PDB code 6gth42) also shows that utilization of the anion-binding site supports the complex formation. These complexes are stabilized by hydrogen bonds and consequently, the affinity and overall activity of these inhibitors are increased. Accordingly, the sulfonate groups of these new diazabicyclooctane inhibitors occupy the anion-binding site discussed here (Supplementary Fig.3)13. In addition, vaborbactam (PDB code 6v7h43) and taniborbactam (PDB code 6sp612) are bound and coordinated in the active site in a similar way. The carboxylate appendage of their oxaborine or benzooxaborine moieties also occupies the anion-binding site10,12,43. Thus, for inhibition of SBLs, it is evident that the anion-binding site of the native enzyme is occupied by the inhibitor, supporting enhanced binding if inhibitors feature a suitable moiety that can bind in this region (Supplementary Fig.3). This anion-binding site represents a very important structural feature of -lactamases, to be considered in future drug development investigations. In this context, our data are unique, as we show via time-resolved crystallography the time course of the displacement of a sulfate ion from this particularly important binding site.

In addition, the oxyanion hole is utilized by a number of inhibitors forming hydrogen bonds with Ser70 NH and Ser237 NH (see Supplementary Fig.4). Furthermore, these structural features are also used in the binding modes of -lactam substrates such as ceftazidime (Supplementary Fig.4h), as well as in multiple other -lactamases.

The obtained refined time-resolved crystal structures provided insight into the molecular kinetics of the binding of boric acid (Fig.3 and Supplementary Fig.5). Starting from the native CTX-M-14 structure, the above-mentioned sulfate and some water molecules (notably OW174, OW352, OW353 and the catalytic OW10) are present in the active site well-defined in the electron density maps. At a delay time of 50ms after mixing the microcrystals with boric acid initially, no additional electron density for the boric acid was observed. Meanwhile, the electron density of the sulfate ion has already changed, indicating a slight shift between the two alternative locations. Initially, in the native enzyme, the alternative positioned sulfate ions refined to occupancies of 47% and 44% for SO4-A and SO4-B, respectively. These change in the 50ms structure to occupancies of 54% for the SO4-A and 41% for the SO4-B position also indicate that initially the position closer to the Ser70 is preferred before the boric acid will covalently bind to Ser70 OG. After a delay time of 80ms, a weak electron density for the bound boric acid (BAB) was observed in the calculated polder map, with a corresponding occupancy of 35%. At the same time, the sulfate ion in the SO4-B position was reoriented by slight translation and rotation so that an oxygen atom has a distance of 2.6 to the O2 hydroxyl group of BAB (Fig.3). The evaluation of the electron density maps revealed that the hydroxyl groups of BAB occupy approximately the same positions as previously occupied by an oxygen of SO4-A and the two water molecules OW352 and OW353. The calculated occupancy for BAB (Fig.5a, Supplementary Table3) and the corresponding electron density increased with longer delay times after mixing, resulting in a well-defined electron density for BAB in the calculated polder map after only 250ms delay time. At this delay time, the occupancy of BAB is already 49%, whereas the occupancy of SO4-A has dropped to 33%. In the further time course investigated, the occupancy of BAB increases only slightly. After a delay time of 10s, it reaches the maximum occupancy of 53%. Even soaking the CTX-M-14 microcrystals in boric acid for 1h could only increase the occupancy to 57%. This indicates that under these conditions the equilibrium of the BAB formation has been reached.

Plots of BAB (a) and GBE (b) with the refined occupancy values obtained in the context of the respective delay times (no linear display), after mixing with boric acid (BA) or glycerol (GOL). The occupancy of BAB increases with prolonged delay time after mixing with boric acid. Subsequent mixing with glycerol causes the BAB occupancy to decrease again, as it is esterified to GBE. The total boron content continues to increase along mixing with glycerol.

Boric acid binds to the active site of CTX-M-14 (Fig.1c) forming an ester with the Ser70 OG. The hydrogen bonding interactions that stabilize the tetrahedral transition state analog during initial binding include the oxyanion hole (Ser70 NH and Ser237 NH). Similar to the binding mechanism of substrates, the nucleophilic attack of Ser70 OG can be supported via activation of the OG by the general base Lys7344. The unprotonated Lys73 side chain can assist in the nucleophilic attack by acting as a general base thereby accepting the proton from the Ser70 OG when the tetrahedral intermediate is formed. A corresponding proposed reaction pathway is shown in Fig.6. Similar to the carboxylate of the acylenzyme intermediate, one hydroxyl group of boric acid (O1) forms hydrogen bonds with the main chain nitrogen atoms of Ser70 (2.8) and Ser237 (2.8), constituting the oxyanion hole (Fig.2b). In contrast to bortezomib and ixazomib, the remaining two hydroxyl groups of BAB do not form hydrogen bonds with Asn170 and Glu16613 (Supplementary Fig.4). In fact, the boric acid is shifted rather in the opposite direction in the anion-binding site, forcing a reorientation of the sulfate ion from the position of SO4-A to the position of SO4-B (Fig.2b), to prevent too close atomic contacts. The boric acid is further stabilized in this position via hydrogen bond interactions of the BAB hydroxyl group (O2) with the hydroxyl group of Ser130 (3.0) and the sulfate ion (SO4-B, 2.6). The third BAB hydroxyl group (O3) forms a hydrogen bond with the water molecule OW10 (2.8). In all observed time steps OW10 remains well-defined in the same position. This water molecule is well-known as the catalytic water molecule mandatory for the deacylating step in -lactam hydrolysis45, initiated by nucleophilic attack on the carbonyl carbon atom of the acylenzyme complex to hydrolyze the acyl bond. It forms hydrogen bonds with the side chains of Ser70 (2.6), Glu166 (2.6), Asn170 (2.5) and BAB (O3, 2.8) (Fig.7). All these intermolecular interactions ensure that BAB is very well coordinated, e.g. a rotational disorder around the Ser70 borate ester linkage is not observed.

Hydrogen bonds are displayed as dashed lines.

The active site of the (a) bound boric acid and (b) glycerol boric acid diester is shown at the 10s delay time point. OW10 is hydrogen bond donor and acceptor to the boric ester of Ser70 (2.6/2.8). The tetrahedral hydrogen bonding pattern of OW10 is completed by Glu166 (2.6) and Asn170 (2.5). Hydrogen bonds of OW10 to GBE are longer than to BAB (2.8/3.2) while the hydrogen bonding pattern with Glu166 (2.5) and Asn170 (2.6) remains similar. The boron atom is positioned at a distance of 3.0 (BAB,
10s) or 3.4 (GBE, 10s) from the catalytic water OW10. Thus, the catalytic water could perform a nucleophilic attack on the boron atom, leading to the reversible hydrolysis of the boric acid serine ester linkage in BAB and GBE. Potential hydrogen bond distances () are indicated by dashed lines.

After monitoring time-resolved structure and dynamics of boric acid binding in the active site of CTX-M-14, we have further investigated the esterification process of boric acid with glycerol. For this purpose, the TapeDrive setup was used again to mix glycerol with CTX-M-14 microcrystals complexed with boric acid beforehand. We defined the delay time 0ms as the starting condition where no glycerol was added, corresponding to the last time point (1h soak) of the serial data collection with boric acid, considering that CTX-M-14 microcrystals were saturated with boric acid (Fig.4 and Supplementary Fig.6). At this defined time point, the occupancy of BAB was refined to 57%. The first change in the electron density of the polder map appears already at the 50ms mixing/delay point. In the region of the BAB hydroxyl groups extending electron density was observed indicating the formation of a glycerol diester. The obtained electron densities allowed the insertion and refinement of a glycerol boric acid diester (GBE), resulting in a GBE occupancy of 26%, while the BAB occupancy remained almost the same with 55%. This indicated also that the formation of the GBE increases the total occupancy of bound ligand in the active site to 81%. The electron density of the sulfate decreased for SO4-A to zero, as the newly formed glycerol diester occupies this position. The alternatively positioned SO4-B fits into the active site together with the BAB and is therefore still present with the same occupancy as the BAB. The observed electron densities at the 80 and 100ms delay times showed only a slight increase for GBE occupancy. A sharp increase in the corresponding GBE occupancy to 51% was observed and refined at the 150ms time point, while in parallel the BAB occupancy dropped to 35% (Fig.5b, Supplementary Table3). By this time, all atoms of GBE are covered with the calculated polder electron density. At the 750ms time point, the entire GBE was well-fitted and covered in the calculated electron density map with a resulting occupancy of 65%. Consequently, since the GBE can no longer act as a hydrogen bond donor for SO4-B due to the lack of hydrogen atoms at the position O2. The sulfate ion is finally completely replaced by a water molecule, OW357, which is accompanied by an increasing GBE and a decreasing BAB occupancy. This correlates with reduced electron density in the SO4 site. The O3 of GBE can also no longer interact with OW10 as a hydrogen bond donor, but only as a hydrogen bond acceptor. GBE approached a refined occupancy of 67% after only 10s delay time, while BAB occupancy dropped to 21%. However, it is interesting to note that the overall occupancy of the ligands (BAB, GBE) bound to Ser70 increased with the observed increase in electron density obtained and refined for the cyclic diester. Thus, the total occupancy of the binding site and region increased from 57%, obtained for soaking only with boric acid, up to 88% when further mixing with glycerol up to a delay time of 10s. The stepwise blocking of the active site by boric acid and the subsequent glycerol diester formation is shown in Fig.4.

Boric and boronic acids have a propensity to form esters with polyalcohols, resulting in the formation of five- or six-membered rings46,47,48. The observed five-membered scaffold of GBE is reminiscent of the autoinducer-2. This borate diester was first observed in complex with the sensor protein LuxP of the marine bioluminescent bacterium Vibrio harveyi49. The triol glycerol can alternatively form both ring systems, with the formation of a six-membered ring being energetically preferred over the five-membered ring, as shown in a computational study46. The investigation of peptidomimetic-boronic acid inhibitors for flaviviral proteases revealed both, a five-membered ring formation of the boric acid moiety and glycerol in the active site for the West-Nile virus NS2BNS3 protease and a six-membered ring formation for the Zika virus NS2BNS3 protease47,48. Despite the high similarity of these enzymes, both ring formations were observed, clearly showing the influence of the individual active site, resulting in a preference due to steric constraints47,48. In the CTX-M-14 active site, glycerol forms a five-membered cyclic diester with two of the three hydroxyl groups (O2, O3) of boric acid that is bound to the active site Ser70 (Fig.2c). A corresponding proposed reaction pathway is shown in Fig.8. The remaining hydroxyl group (O1) of the boric acid maintains the stabilizing hydrogen bonds with the main chain nitrogen atoms of Ser70 (2.9) and Ser237 (3.0) in the oxyanion hole (Fig.2c). During the esterification the sulfate ion in the anion-binding site is finally replaced by a water molecule (OW357) that forms alternative hydrogen bonds with the cyclic diester O1 (2.7) and the hydroxyl group of Thr235 (2.8) (Fig.2c). The other oxygen of the cyclic diester O3 forms a hydrogen bond with OW10 (3.2), which itself is strongly coordinated by Ser70 (2.8), Glu166 (2.5) and Asn170 (2.7). The remaining free hydroxyl group of GBE (O4) forms an additional hydrogen bond with the amide side chain of Asn132 (3.0) and weak hydrogen bonds with amide side chains of Asn104 (3.5) and Asn170 (3.5) (Fig.2c). In that conformation all oxygen atoms of the GBE are coordinated via hydrogen bonds either directly with the enzyme or via a water molecule. This is probably also the reason for the preference of the five-membered over the six-membered cyclic diester in the CTX-M-14 active site. In a six-membered ring, the free hydroxyl group could not form hydrogen bonds with Asn132 because it would be located in the center of the molecule. In fact, there would probably be no side chain for possible hydrogen bond interactions with the free hydroxyl group in that orientation as it would point out of the active site. Thus, the formation of a hydrogen bond of the free hydroxyl group of GBE with Asn132 is probably the determining factor, explaining our observation of only five-membered cyclic diester formation in all obtained GBE structures.

Hydrogen bonds are displayed as dashed lines.

The central carbon atom of the glycerol diester with boric acid becomes a stereo center with S-configuration. Also, the boron atom of GBE is a stereo center with S-configuration. Both stereocenters are observed without any racemic disorder. This is probably an indication for the specific active site environment of the -lactamase. For example, proteinase K has weak specific substrate preferences and glycerol forms a simple monoester with the boric acid bound to the active site serine (PDB code 2id850). Obviously, the stepwise formation of a monoester and diester is much too fast to be observed with our experimental setup.

As expected, the covalent binding of boric acid and the boric acid diester to the catalytic Ser70 in the active site of CTX-M-14 -lactamase resulted also in the inhibition of the enzyme17,18. Boric acid remains in the active site of the -lactamase in the crystal lattice with an occupancy of 57% even after prolonged soaking. Consequently, it can be concluded that the boric acid diester does not dissociate over time and therefore inhibits the enzyme (in the crystal lattice) for a certain period if the solvent conditions are unchanged. To quantify the effect of the observed occupation of the active site,
enzymatic activity assays applying a photometric determination of the 50% inhibitory concentration (IC50) values were performed. Moderate IC50 values of 2.90.4mM for boric acid and 3.10.4mM for the combination of boric acid with glycerol were determined (Supplementary Fig.7). Interestingly, the IC50 values are quite similar even though the crystallographic data showed a higher occupancy of the GBE in the crystal lattice, which would imply a higher inhibition. Compounds that are considered as inhibitors usually have substantially lower IC50 values, therefore the boric acid and the glycerol diester at this point cannot be considered as effective -lactamase inhibitors. This is in line with the observed incomplete occupancy of the boric acid and its glycerol diester in the crystal structures and the potentially reversible binding of boric acid. The organization of the active site in the endpoint complexes may also indicate that reversible mechanism for the dissociation of the inhibitor. The boron atom is positioned at a distance of 3.0 (BAB, 10s) or 3.4 (GBE, 10s) from the catalytic water OW10 (Fig.7). Thus, the catalytic water is well positioned to perform a nucleophilic attack on the boron atom, leading to the reversible release of boric acid or the GBE. Reversible inhibitors have the advantage of not being depleted or modified by their target, thereby enabling their capacity to inhibit several enzymes during their lifetime. Our data highlight the potential of boric acid derivatives in medicinal chemistry.

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Time-resolved crystallography of boric acid binding to the active site serine of the -lactamase CTX-M-14 and ... - Nature.com

‘A Family Affair’ Review: Nicole Kidman and Zac Efron Have Zero Sparks – Observer

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Nicole Kidman and Zac Efron in A Family Affair. Aaron Epstein/Netflix

In Hollywood, the industrys very particular rules of math state that two attractive movie stars should result in at least a semblance of onscreen chemistry. Its worked for all kinds of bizarre pairings, and it should have worked for Nicole Kidman and Zac Efron, teaming up in A Family Affair for the second time. Kidman is a skilled actor with incredible range and a willingness to take risks on potentially bad projects, and Efron is chiseled, talented and always game for ridiculous comedic scenes centered on self-ridicule. Although separately magnetic and successful in 2012s The Paperboy, together here the actors fumble for any draw.

A FAMILY AFFAIR 1/2(1.5/4 stars) Directed by: Richard LaGravenese Written by: Carrie Solomon Starring: Nicole Kidman, Zac Efron, Joey King, Kathy Bates, Liza Koshy, Wes Jetton, Sherry Cola Running time: 114 mins.

In the film, Efron parodies himself as Chris Cole, a self-absorbed, muscled movie star best known for starring in an action franchise called Icarus Rush. Hes vain, disconnected and apparently hasnt been in a grocery store in decades. He is constantly breaking up with girlfriends with the help of consolation diamond earrings and his assistant Zara (Joey King), a frazzled young woman who wants to be producing movies despite being in her early 20s and having no experience. Chris is so temperamental and childish that he vacillated between threatening to fire Zara and desperately needing her to get him protein powder from the grocery store he cant visit himself.

Zara finally hits her limit with Chris inane antics and quits, reluctantly telling her highly successful writer of a mom Brooke (Kidman) that shes now out of a job. Brooke has been single since the death of Zaras dad, often confiding her woes in her mother-in-law Leila (Kathy Bates), who appears to be some kind of famous photographer. When Chris shows up at Brooke and Zaras house trying to woo Zara back to work, he ends up bondingand drinking tequilawith Brooke. Its an odd dynamic, especially since screenwriter Carrie Solomon and director Richard Lagravenese have already established Chris as a selfish dipshit. Its hard to understand what Brooke, who quotes Greek mythology and is potentially the hottest MILF on planet Earth, sees in him beyond his biceps. But whatever it is, its enough to get them into bed, where Zara immediately discovers them and knocks herself out on the doorway.

The rest of the film is a requisite story about redeeming oneself and making relationships work. You already know the ending without having seen it, although its a moderately entertaining diversion to get there. Brooke gets her groove back (this makes for a good double feature with Anne Hathaways recent rom-com The Idea of You), Chris gets to make a human connection (and go to a grocery store) and Zara gets to skip years of paying her dues to unrealistically ascend the Hollywood ladder. It aims for emotional sincerity in moments and there are some laughs, thanks mostly to King and Efrons dynamic, but its mostly a surface-level fantasy about two successful, pretty people who find love. The hurdle in their way isnt the massive age gap or Chris unwieldy celebrity, but Zaras disapproval and whining. Its all a bit flimsy on paper, although its easier to overlook the gaping cracks in the narrative when youre actually watching Kidman do her thing.

The challenge here is that Kidman and Efron have no spark, which makes it awkward and uncomfortable to witness their coupling. No wonder Zara feels so much ick at the prospect of Brooke and Chris getting together. Its also difficult to reconcile Chriss terrible behavior with him becoming a leading man love interest for a woman as smart and worldly as Brooke. But this is a fantasy where everyone gets what they want, even if that in no way aligns with reality. It worked in The Idea of You, a better version of this story, but here you just want Brooke to find a guy who doesnt need the Icarus myth explained to him. Its ultimately this lack of chemistry that keeps A Family Affair from transcending an existence as a Lifetime movie aired on Netflix.

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'A Family Affair' Review: Nicole Kidman and Zac Efron Have Zero Sparks - Observer

All-metal aromatic ring isolated for the first time – Chemistry World

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A four-atom bismuth species is the first all-metal ring with aromatic bonding character to have been isolated in the lab. The structure was synthesised by researchers in Germany, who say that their findings raise important questions about the nature of aromaticity in materials composed of heavier elements.

Despite having been studied for almost 200 years, aromaticity remains one of chemistrys most enigmatic phenomena. At school, almost every student will learn about aromatic carbon rings like benzene, but attempts to make analogous compounds entirely from metal atoms have proven much more difficult. In 2001, the aromatic all-metal species Al42 was detected spectroscopically, while the antiaromatic Al44 was detected in 2003. However, the only aromatic metal rings including gallium, gold and thorium species to have been isolated in the lab have needed to be stabilised by covalently bonded non-metal substituents.

Now, a team led by Florian Weigend at Philipps-University Marburg and Lutz Greb at Heidelberg University has isolated a cationic Bi44+ aromatic ring. The species takes the form of a planar rhomboid and is trapped non-covalently between two shells that each feature an indium bromide core bound within a cyclic ligand containing four pyrrole units.

The researchers note that the Bi44+ ring is isoelectronic with the antiaromatic Al44 species. They argue that this suggests that the charge distribution around an ionic aromatic metal ring can influence whether it will take on aromatic or antiaromatic bonding character. The team note that this finding complicates discussions of the Hckel model of aromaticity a concept that they note is valid for second-row elements but less deterministic for the heavier congeners.

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All-metal aromatic ring isolated for the first time - Chemistry World

Bron Breakker On His Chemistry With Baron Corbin In NXT: ‘We Hit It Off Immediately’ – 411mania.com

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Bron Breakker says he really enjoyed working with Baron Corbin during their tag team run in NXT. Breakker and Corbin teamed up as The Wolf Dogs from late last year until they moved to the main roster, and Breakker talked about working with the veteran in an interview with Cameron Hawkins on The Ringer.

Baron and I had hit it off from the get-go, Breakker said (per Fightful). As soon as he came down to NXT, we hit it off immediately. It was really cool for me to be able to get to work with him because obviously, it brought out a different side of me where I was being a little bit more entertaining, just being funny, just goofing off. We both were just loving it and having a great time.

Breakker will face Sami Zayn for the WWE Intercontinental Championship tomorrow at Money in the Bank in Toronto.

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15 Actor Duos With Unmatched On-Screen Chemistry – BuzzFeed

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And all the true fans know that this wasn't Zac and Nicole's first movie together...or even their first time playing love interests. The duo first starred opposite each other in the 2012 thriller The Paperboy. So, here are 15 more celebrity duos that have such great chemistry they've played love interests more than once: 1. Timothe Chalamet and Saoirse Ronan have been in three movies together and played love interests in two: Lady Bird (2017) and Little Women (2019), both directed by Greta Gerwig. 2. Emma Stone and Ryan Gosling have played love interests in all three movies they starred in together: Crazy, Stupid, Love (2011), Gangster Squad (2013), and La La Land (2016). 3. Amy Adams and Christian Bale played opposite each other as love interests in American Hustle (2013) and Vice (2018). 4. Javier Bardem and Penlope Cruz played opposite each other in four movies: Jamn, Jamn (1992), Vicky Cristina Barcelona (2008), Loving Pablo (2017), and Everybody Knows (2018). 5. Adam Sandler and Drew Barrymore have played love interests in three movies: The Wedding Singer (1998), 50 First Dates (2004), and Blended (2014). 6. Jennifer Aniston has also starred alongside Adam Sandler in several movies, and they've played love interests three times in the movies Just Go With It (2011), Murder Mystery (2019), and Murder Mystery 2 (2023). 7. Sanaa Lathan and Omar Epps played love interests in both movies they starred in together: The Wood (1999) and Love & Basketball (2000). 8. Kristen Stewart and Jesse Eisenberg have starred opposite each other as love interests in three movies: Adventureland (2009), American Ultra (2015), and Caf Society (2016). 9. Tom Hanks and Meg Ryan have played love interests in all four movies they've starred in together: Joe Versus the Volcano (1990), Sleepless in Seattle (1993), You've Got Mail (1998), and Ithaca (2015). 10. Jennifer Lawrence and Bradley Cooper have been in four movies together, but only played love interests in two: Silver Linings Playbook (2013) and Serena (2014). 11. Matthew McConaughey and Kate Hudson played opposite each other as love interests in How to Lose a Guy in 10 Days (2003) and Fool's Gold (2008). 12. Kate Winslet and Leonardo DiCaprio have played opposite each other as love interests in Titanic (1997) and Revolutionary Road (2008). 13. Winona Ryder and Keanu Reeves starred as love interests in three of the four movies they've done together: Bram Stokers Dracula (1992), A Scanner Darkly (2006), and Destination Wedding (2018). 14. Eugene Levy and Catherine O'Hara have played a couple in Best in Show (2000), A Might
y Wind (2003), and Schitt's Creek (20152020). 15. Finally, Jennifer Garner and Mark Ruffalo play opposite each other as love interests in 13 Going on 30 (2004) and The Adam Project (2022).

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Tang looks to build team chemistry after roster completion – The Mercury – Manhattan, Kansas

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With the addition of Illinois big man Coleman Hawkins late last month, Kansas State head coach Jerome Tang and his staff wrapped up their roster for the upcoming season. And unlike the previous two years, the coaches got their work done early this year, leaving the rest of the summer for the 10 newcomers on the roster to begin to mesh.

This is the first time weve had our whole roster done in June, Tang said. Our first year, Keyontae (Johnson) didnt show up until August right when school started, and Desi (Sills) didnt get her until October. And then last year, we didnt get a couple of guys until August or September and Will (McNair Jr.) was right after school started. So, were gonna get to spend the whole four weeks in July of workouts with the whole group here. I believe thats gonna make a huge difference in how we develop as a team.

K-State brings in eight Division I transfers, one junior college transfer and one high school recruit to joing senior David NGuessan and sophomore Taj Manning and Macaleab Rich.

Because the Wildcats dont have a large base of returners, the need to create team chemistry among all of the disparate parts becomes even more crucial during this summer period.

It has to happen organically, but we have to create opportunities for it to happen, Tang said. They all live in the same apartment complex. And its 30 seconds from the gym and we spend a lot of time in the gym. We have family dinners. So, were always together in each others homes. We create opportunities for organic chemistry, just for guys to be able to interact with each other in different situations. Its our job to connect with our players hearts.

And once you connect with their hearts, you can get them to understand or at least youll understand where theyre coming from to help them get to where they want to get to.

The rosters make up features multiple athletic and versitile bigs, led by Hawkins along with Daivd NGuessan, Achor Achor (Samford) and Ugonna Onyenso (Kentucky) and Baye Fall (Arkansas).

When NaeQwan Tomlin was dismissed from the team in the middle of last season, K-State found itself short on reliable big men. That should not be an issue this season.

The way the game is played now, the really talented bigs who want to play in the NBA have to play in the 5-out type offenses and do multiple things, Tang said. They no longer just let guys stand on the block anymore. So, knowing the type of talent we wanted to attract, we had to run an offense that fits that personnel.

We can help them get to where they want to get to and because weve done that (in the past) and its given us this opportunity to be able to recruit guys like Coleman, Achor (Achor) and Ugonna (Onyenso).

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Tang looks to build team chemistry after roster completion - The Mercury - Manhattan, Kansas

Diastereodivergent nucleophilenucleophile alkene chlorofluorination – Nature.com

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Our strategy drew inspiration from our electrochemical hypervalent iodine-mediated syn-difluorination of alkenes14, where two fluorides sequentially invert a proposed iodonium intermediate (Fig. 1d). Electrochemical oxidation of iodotoluene provides a controllable and sustainable method for the generation of the difluoro(tolyl)-3-iodane (IF2) mediator. Switching the electrochemical oxidation off and then adding in the substrate (ex-cell approach) was found to better facilitate tolerance to oxidatively sensitive substrates that contain electron-rich functionality14,22,23,24. This is because there is no residual oxidant in solution to decompose the substrate. Wishing to exploit the same electron-rich chemical space, we adopted the ex-cell electrochemical method for generating IF2 and deliberately chose oxidatively sensitive 1a as the model substrate (Fig. 2a). This substrate deliberately contains an unactivated acyclic internal alkene, which is an underexplored alkene-type in fluoro- or chloro-functionalization reactions25,26,27,28,29,30. Adapting our difluorination conditions by adding an excess of various R4N+ chloride salts to a solution of 1a and IF2 in 5.6HF:amine (1:1 (v/v) mixture of 3HFNEt3 and 9HFpy) in dichloromethane (DCM)hexafluoroisopropanol at room temperature led predominately to alkene dichlorination. Without hexafluoroisopropanol, the use of 1equiv. of chloride provided more selective conditions but, surprisingly, not for the expected syn-addition product, 1d or 1e, rather to the anti-addition product, 1b. Nevertheless, we observed six out of the eight possible products (1g and 1h were not observed) (Fig. 2a), confirming the substantial challenge of controlling chemo-, regio-, and diastereoselectivity in the reaction.

For full details, see Supplementary Tables 15. a, Challenges with NuNu chlorofluorination to control chemo-, regio- and diastereoselectivity. Reaction of model compound 1a to products 1bi (n/o, not observed) using the ex-cell electrochemical approach. b, Chemoselectivity with different chloride sources. c, Temperature dependence on regioselectivity for anti-addition. d, Diastereoselectivity switch with changing nHF:amine ratio. e, A summary of the diastereoselectivity switch. IF2 generation: p-iodotoluene in 5.6HF:amine and DCM (13mA, 2.2F, divided cell, Pt||Pt). Anti conditions: alkene (0.6mmol), IF2 (1 equiv.) solution in 5.6HF:amine, NEt4Cl (1 equiv., 0.2 equiv.h1), DCM, 46C, 16h; syn conditions: alkene (0.6mmol), IF2 (1 equiv.) solution in 5.6HF:amine adjusted to 7HF:amine, NEt4Cl (1 equiv., 0.2 equiv.h1), DCM, 46C, 16h.

A range of different chloride salts were tested (Fig. 2b); chloride with inorganic cations led to more dichlorination, and more soluble organic cations led to greater selectivity for chlorofluorination, with NEt4Cl giving the highest yield (Supplementary Table 1). The regioselectivity of the anti-addition product could be improved by lowering the temperature, with 46C (CO2(s) in MeCN) providing the best balance of selectivity and yield (Fig. 2c). By adding chloride slowly, the competing dichlorination could be attenuated, leading to an optimized 85% yield of the anti-addition product 1b with a regioisomeric ratio (r.r.) of 12:1 (Fig. 2e).

During these efforts, product 1d from syn-chlorofluorination was only observed in trace quantities (<5%). However, when we started to increase the nHF:amine ratio beyond 5.6 (by adding 9HFpy to the 5.6HFamine mixture), the diastereoselectivity started to shift. A range of nHF:amine ratios were tested (Fig. 2d), which revealed the mechanism could be flipped with this highly sensitive trigger; increasing the ratio from just n=5.6 to just 7 was sufficient to completely switch the diastereoselectivity, yielding the syn-addition product 1d in good yield and excellent r.r. (Fig. 2e). Although the selectivity enhancement was maintained at ratios above 7HF:amine, the yield dropped, and therefore, optimized conditions for the syn-chlorofluorination of internal, unactivated alkenes remained with 7HF:amine (Supplementary Table 4).

To explore the generality of the reaction, a wide selection of alkene substrates was probed under the conditions (Table 1). Terminal alkenes transformed efficiently under the anti-addition 5.6HF:amine conditions, giving good to excellent yields and selectivity for the 1-chloro-2-fluoro products (nj). Oxidizable functionalities, such as secondary and tertiary amines, alcohols, anilines and styrenes and more complex molecules, were all well tolerated. Remarkably, the expected 1-chloro-2-fluoro (nj) regioselectivity was not observed for the cinchonine 11a, as the 1-fluoro-2-chloro regioisomer 11k preferentially formed, which is probably due to the internal position being sterically more inaccessible than all other substrates.

The anti-chlorofluorination conditions were then successfully applied to a broad range of internal alkenes, including cis and trans acyclic and cyclic alkenes, as well as substituted and electron-poor alkenes (Table 1). Although oxidants (Selectfluor and meta-chloroperoxybenzoic acid) previously used for IF2 formation were found to be inferior (Supplementary Table 8), we found that commercially available (bis(trifluoroacetoxy)iodo)benzene (PIFA) led to only a small drop in yield (73% versus 85% for 1b), which represents a practical alternative to electrochemically generated IF2. Oxidizable and acid-sensitive (29b, 34b and 35b) functional groups were well tolerated, and the yields were good to excellent in all cases. High regioselectivity was observed with fluoride placed on the site best able to stabilize a positive charge, hence, further away from electron-withdrawing groups. Exquisite regioselectivity was observed even four bonds away from a tertiary amine (27b). When there are competing factors for positive charge stabilization (24b) or the alkene is more remote (23d), then the regioselectivity decreases or disappears. Biologically relevant compounds were also transformed, including glucal derivative 35b and cholesterol 28b. Finally, a multigram scale-up of 39b was successfully demonstrated.

Previously reported chlorofluorination conditions are ENu methods that combine an N-chloro electrophilic chlorine reagent (N-chlorosuccinimide (NCS)31,32,33,34, trichloroisocyanuric acid (TCCA)35, N-chlorosaccharin36) with a source of HF37, and all lead to exclusive anti-addition. With few exceptions32, these conditions are demonstrated on limited compound classes, for example, styrenes, and without complex functionality, especially that which is easily oxidized. Hence, we were intrigued to test the complementarity to our NuNu system on substrates containing more varied functionality and alkene-types (Table 1). In all cases, isolated yields from our NuNu conditions proved superior to the nuclear magnetic resonance (NMR) yields from reported procedures, including both cis and trans internal alkenes, electron-poor alkenes and terminal alkenes. The regioselectivity either matched or was superior to the reported conditions.

The scope of the alkene syn-chlorofluorination reaction was then probed (Table 2). Various hetero-cyclic and aliphatic homo-allylic amines afforded the desired products in moderate to very good yields, with excellent tolerance for oxidatively sensitive functional groups. Cis alkenes underwent the syn-addition with generally higher efficiency than trans alkenes
(40d versus 40b). When the yields are moderate, oxidative decomposition probably competes. The anti-addition pathway was strongly attenuated under these conditions, which ensured the diastereoselectivity was excellent throughout. The regioselectivity was also excellent, with an overwhelming preference for the chloride to be placed nearest to nitrogen. Finally, ester 38a also underwent the syn-chlorofluorination.

To rationalize the synthetic results and, in particular, the origin for the regioselectivity and the intriguing switch in diastereoselectivity, we conducted a series of mechanistic experiments. Using 40a as a model substrate, alkene activation with iodane was calculated to occur most favourably by forming an iodine(III) complex, as opposed to the commonly invoked iodonium intermediate (Supplementary Fig. 42)38. To identify the specific iodane species responsible for each mechanism, we calculated energetic barriers for iodine(III) complex formation (Fig. 3a). IFCl was found to have the lowest energy barrier for alkene activation, whereas the transition state with ICl2 is completely inaccessible at 46C. The enhanced reactivity of IFCl over IF2 and ICl2 was also supported by charge and orbital coefficient calculations (Supplementary Fig. 48 and Supplementary Table 18). These findings were consistent with experimental reactivity studies using preformed iodanes (Fig. 3b). When a sample of ICl2 was applied to 1a under the anti conditions (Fig. 3b1), only trace product 1b was formed, confirming that ICl2 cannot be an active iodane and a more reactive species is required. However, when a 50:50 mixture of ICl2 and IF2 was used in the reaction the reactivity switched back on and product 1b formed readily (Fig. 3b2). These stoichiometries support IFCl to be responsible for anti-addition, which is notable considering fluoro-chloro-aryl iodanes have extremely limited presence in literature, with only one report proposing it as a potential intermediate39, in contrast to aryl dichloroiodanes, which are established reagents for alkene dichlorination15,40,41,42. Speciation studies (1H NMR; Supplementary Figs. 26 and 27) of IF2 with added NEt4Cl (01equiv.) and IF2 mixed with ICl2, conducted at 46C, revealed the appearance of a new species that we propose is consistent with the formation of IFCl. Density functional theory (DFT) calculations modelled at 46C also demonstrated IFCl was readily accessible from either IF2 or ICl2 via two possible mechanisms (Supplementary Figs. 51 and 52 and Supplementary Scheme 5).

a, DFT calculations modelled at 46C of iodine(III) complex formation, showing IFCl is the most reactive. Level of theory: M06-2X/6-31+G(d)/LANL2DZ(I)+SMD(CH2Cl2)//M06-2X/def2-TZVP+SMD(CH2Cl2). b, Reactivity studies using preformed samples of IF2 and ICl2 to establish the active iodane under each set of conditions. Anti-addition to 1b is not observed with ICl2 alone but is with 50:50 IF2:ICl2, providing evidence for IFCl to be the active iodane for anti-addition. Syn-addition to 1d does not predominate in the presence of ICl2 and only forms with IF2, providing evidence for IF2 to be the active iodane for syn-addition. c, Natural Bond Orbital (NBO) calculations (DFT) of iodine(III) complex to establish regioselectivity of nucleophile attack. d, Consideration of which halide attacks first. For syn-addition, fluoride attacks first and for anti-addition, chloride attacks first. eg, Anti-addition mechanisms discounted due to unfavourable transition state energies. The energies refer to the following starting materials: 40a in e, cis-but-2-ene in f, 40a in g. h, DFT calculations for the proposed mechanism for anti-addition, which shows a favourable transition state energy for a 1,2-chloride shift.

Under syn-conditions, the active iodane cannot be IFCl, considering anti-addition predominated with a 50:50 mixture of ICl2 and IF2 (Fig. 3b3). Syn-addition occurred only when IF2 was used with slow addition of chloride (Fig. 3b4), indicating IF2 to be the active species. As it is established syn-difluorination occurs through IF212,13,38, we reasoned the levels of difluorination (in the absence of chloride) should mirror those of syn-chlorofluorination (in the presence of chloride) when the nHF:amine ratio is altered. Indeed, a direct match of products 1i and 1d is observed (Supplementary Fig. 40), with 7HF:amine giving the highest yields of both products, suggesting IF2 to be the active iodane for syn-chlorofluorination. An explanation for the current limitation of syn-chlorofluorination to homo-allylic amines was revealed by DFT calculations of iodine(III) complex formation with IF2 (Supplementary Fig. 49); while a barrier of 19.2kcalmol1 was calculated for homo-allylic amine, which is approaching the limit of accessibility at 46C, a barrier of 23.3kcalmol1 was calculated for the corresponding bis-homo allyl amine, which is inaccessible.

To understand the regioselectivity, we undertook natural population analysis calculations (Fig. 3c). A clear difference in charge distribution between the alkenyl carbons is indicated, with the carbon distal to nitrogen more electropositive and, therefore, more reactive towards nucleophilic attack. Transition state calculations predict fluoride and chloride attack onto activated alkene 48aIF2 to be rapid and facile (Supplementary Fig. 47). Hence, we propose syn-addition occurs when fluoride attacks first, followed by a subsequent chloride attack (Fig. 3d).

Formation of the anti-addition product is less obvious. Although chloride attack onto the more electropositive distal carbon occurs very readily and with a low barrier to form INT1 (Fig. 3c and Supplementary Fig. 47), this was initially discounted because it is not consistent with the observed major regioisomer, which places chloride on the proximal carbon. Several inferred mechanisms in literature were considered, including direct chloronium formation, that is, alkene attack of a Cl+ equivalent (Fig. 3e)41,43, syn-ligand-coupling with fluoride attacking first (Fig. 3f)44 and syn IX addition followed by fluoride or chloride attack (Fig. 3g)45,46,47,48. In each case, we considered different chlorinated or fluorinated iodanes and coordinated HF environments (Supplementary Figs. 4447). Of these pathways, only the syn IF addition pathway (Fig. 3g) was found to be energetically feasible. However, this pathway was discounted, because the competing chloride attack on the iodine(III) complex to form the chlorinated-iodanated intermediate (INT1) is far more favourable (Supplementary Fig. 47). A kinetically accessible transition state from INT1 was located for a 1,2-chloride shift with Brnsted acid (HF) activation of the fluoride nucleofuge (Fig. 3h and Supplementary Fig. 43). Incipient chloronium formation through displacement of the iodane (from INT1 to INT2) is followed by very rapid and exergonic attack by fluoride (TS2). Although this pathway for chloronium formation has been offered as a potential mechanism for alkene dihalogenation4, to the best of our knowledge, no examples with theoretical or experimental evidence have been reported. Hence, our proposed pathway for anti-addition is consistent with the observed regio-, chemo-, and diastereoselectivity, the barrier height is consistent with the observed reaction rates, and it is the only pathway that can explain the formation of each iso
mer of compound 35b (Supplementary Figs. 3639).

Since the identity of the halide that attacks the iodine(III) complex first is diastereo-determining, we were inspired to understand how the reaction conditions differed to facilitate this. Hence, several fundamental physical characteristics were measured of the 5.6 and 7.0HF:amine solutions, including the concentrations of fluoride (F) and HF (Fig. 4a). Despite distinct reaction outcomes under each set of conditions, only the equivalents of HF substantially differed. However, when the number of equivalents of HF in 5.6HF:amine were matched to that of 7.0HF:amine (that is, to 204), no syn-chlorofluorination was observed (Supplementary Table 13). Therefore, it cannot solely be the identity of the iodane and manipulation of the equilibrium between ICl2, IFCl and IF2 that dictates the diastereoselectivity.

a, Analysis of the physical characteristics of each medium, which do not show a substantial difference between them. b, Assessment of the difference in nucleophilicity of fluoride in 5.6HF:amine and 7.0HF:amine by measuring the kinetics of the fluorination of p-nitrobenzyl bromide in each medium. The lines through plotted data are modelled second order fits. c, Assessment of the difference in nucleophilicity of chloride in 5.6HF:amine and 7.0HF:amine by measuring the kinetics of a chlorination reaction in each medium, which shows a lower nucleophilicity in 7.0HF:amine. The lines through plotted data are modelled second order fits. d, A diastereoselectivity switch can be achieved by controlling the concentration of chloride. e, A summary of the diastereodivergent NuNu alkene chlorofluorination mechanisms. The bifurcation of mechanisms is dependent on the concentration and the relative nucleophilic activity of chloride and fluoride ions, which in turn dictates the structure and reactivity of the iodane, which halide adds first to the alkene, and the mechanism of iodane displacement.

The relative nucleophilicities of chloride and fluoride were next compared under both sets of conditions by measuring bimolecular nucleophilic substitution displacement rates in appropriately chosen transformations. The rate of reaction between p-nitrobenzyl bromide and fluoride proceeded at similar rates in both HF:amine solutions (Fig. 4b), indicating that fluoride has a similar nucleophilicity under each conditions. However, when chloride competes with fluoride in the substitution of n-butyl mesylate under both sets of conditions, the rate of chlorination was found to be 3.6 times faster in 5.6HF:amine compared with 7.0HF:amine, and no fluorinated product was observed (Fig. 4c). Nucleophilicity calculations of chloride and fluoride ion clusters also mirror these experimental observations (Supplementary Figs. 5355). Combined, these data suggest that the dampened nucleophilicity of chloride in 7.0HF:amine promotes syn-chlorofluorination by allowing fluoride to add first, but in 5.6HF:amine, chloride has higher nucleophilicity and promotes anti-chlorofluorination by adding first.

Increasing the chloride concentration in 7.0HF:amine, via a single portion addition at the reaction outset, reversed the product outcome back to anti-addition product 1b (Fig. 4d). This evidence adds further support to the diastereodivergence being controlled by which nucleophile attacks first; if chloride is in sufficiently high concentration or is sufficiently nucleophilic, then the more reactive IFCl is formed, and chloride can attack the alkene first, resulting in anti-chlorofluorination via a 1,2-chloride shift. Otherwise, fluoride adds first to an IF2-activated alkene and syn-chlorofluorination is achieved, following nucleophilic substitution by chloride (Fig. 4e).

In summary, we have developed a NuNu strategy for the chlorofluorination of unactivated alkenes, which selectively gives either anti- or syn-addition. Good to excellent yields of products, including those that are electron-rich and readily oxidizable, are provided with very high regio-, chemo- and diastereoselectivity. A simple switch was discovered for transitioning between anti-and syn-chlorofluorination based on the HF:amine ratio used in the solution. Mechanistic studies revealed that different iodanes promote each pathway but that the identity of the halide adding to the alkene first is diastereo-determining, with fluoride leading to syn-addition and chloride leading to anti-addition. The anti-addition pathway follows an unusual 1,2-chloride shift followed by rapid fluoride addition from iodane. These results represent an important advance in the application of hypervalent iodine for the vital elaboration of fluorinated motifs in an ever-expanding chemical landscape, and show how capitalizing on a subtle and simple variation of reaction solvent composition can influence product selectivity.

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Diastereodivergent nucleophilenucleophile alkene chlorofluorination - Nature.com

Alchivemycin A synthesized with help from enzymes – Chemical & Engineering News

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Alchivemycin A, a molecule produced by Streptomyces bacteria, has interesting antimicrobial properties that scientists would love to study for cues on how to make better antibiotics. But every previous attempt to assemble it in the lab was stymied by the molecules structural complexity. The trickiest bits include a highly oxidized macrocyclic core and an unusual 2H-tetrahydro-4,6-dioxo-1,2-oxazine (TDO) ring.

Now, Xiaoguang Lei of Peking University and coworkers have overcome the challenge by looking to nature. The researchers used enzymes from the molecules biosynthetic pathway to carry out three selective late-stage oxidations needed to finish the synthesis (Nat. Synth. DOI: 10.1038/s44160-024-00577-7). The team has been trying to make the molecule for a decade, and its exciting to have finally done it, Lei says in an email.

The 25-step synthesis relies on traditional chemical methods such as Suzuki coupling and nucleophilic substitution to assemble the macrocyclic skeleton. Then its the enzymes turn to add the finishing touches. The two epoxide-installing enzymes, AvmO2 and AvmO3, gave excellent yields right away despite the unnatural substrate, which Lei says was a pleasant surprise. The enzyme responsible for the final step, inserting an oxygen into a lactam to turn it into the elusive TDO ring, needed a little bit of extra engineering for efficiency. Switching a tyrosine for an arginine did the trick, getting the yield of the final step up to 85%.

Integrating enzymes into organic synthesis is becoming increasingly popular, so Lei and coworkers use of biocatalysis isnt inherently novel, says Han Renata, who researches chemoenzymatic synthesis at Rice University, in an email. But he says this study is a well-executed illustration of how enzymes can help chemists tackle daunting targets.

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Alchivemycin A synthesized with help from enzymes - Chemical & Engineering News

In memoriam: Daniel Atkinson, 102, UCLA professor and pioneer in field of metabolic biochemistry | UCLA – UCLA Newsroom

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Daniel E. Atkinson, a professor of chemistry and biochemistry at UCLA for nearly 40 years who was recognized internationally for his seminal contributions to metabolic biochemistry, died Feb. 2 at his home in Medford, Oregon. He was 102.

Atkinson was just the second biochemist appointed to what is now the UCLA Department of Chemistry and Biochemistry, in 1952. He retired in 1991 but remained active in the UCLA community until moving to Oregon in 2011. Over the years, he trained more than 30 doctoral students in his laboratory, as well as over 20 postdoctoral fellows and visiting faculty.

In his research Atkinson authored more than 90 published studies with his students he pioneered the field of metabolic regulation. His work allowed for the development of the concept of energy charge, which today is a main topic in biochemistry textbooks. He was also responsible for our present understanding of the biological role of the urea cycle in pH regulation.

Atkinsons acclaimed 1977 monograph Cellular Energy Metabolism and its Regulation, is still widely read in the field. In a 2005 review, John Duncan wrote that anyone wanting a readable introduction to the classic ideas of metabolic regulation could scarcely find a better place to start. And in a 2013 review, Ralph Osgood wrote that Atkinson was a pioneer in the field of biochemistry and that the book still had a touch of delicious heresy. A great book still, many years later, from a great scientist.

Read the full obituary on the UCLA Department of Chemistry and Biochemistry website.

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In memoriam: Daniel Atkinson, 102, UCLA professor and pioneer in field of metabolic biochemistry | UCLA - UCLA Newsroom